1. Field of the Invention
This invention generally relates to the accurate measurement of phase difference between a pair of alternating current input signals. It is particularly adapted for use at high frequencies where one or both of the input signals is pulsed.
2. Related Prior Art
There are, of course, many known circuits for measuring phase difference between alternating current signals. A special subclass of such known circuits is also known for measuring the phase of pulsed high frequency signals. For example, reference may be had to the following publications:
1. Fox et al, "A Microprocessor Controlled Phase Measurement System For 2856 Mhz Pulses," 1982 IEEE MTTS International Microwave Symposium, Dallas, Tex., June 15-17, 1982, SLAC-PUB 2902, April 1982, 3 pages. PA1 2. Aertech, "Polar Discriminators," a five-page sales brochure.
Fox et al specifically relates to the measurement of phase difference between pulsed high frequency signals. Such circuits are used, for example, for supervision of radar installations as well as for controlling pulsed high-frequency signals often used in linear accelerators and synchrotons for high energy physics applications. The Fox et al circuit uses phase shifters and mixers as well as related signal processors and is therefore relatively expensive--and temperature dependent with respect to several components distributed throughout the measurement circuit (e.g., mixers, phase shifters, etc).
Aertech uses a set of matched quadrature couplers and square law detectors to produce analog signals which may be used to control the x,y coordinates of an oscillograph so as to produce a polar coordinate display where the radius of a vector is proportional to amplitude and the angular location of the vector is proportional to the phase difference between two input signals.
There remains, however, need for a relatively efficient and highly accurate phase measurement method/apparatus which may utilized for high frequency pulse signals and which provides accurate outputs easily used in following analog or digital circuits.